Accelerometer



oct. 11, 1949.

c. M. HATYHAwAY AocELERoMETER Filed April 5, 1945 [N VEN TOR.

Patented Oct. 11, 1949 UNITED STATES PATENT OFFICE 8 Claims.

The present invention relates to an acceleration recording apparatusmore commonly known as an accelerometer.

In certain types of vehicles and craft it is desirable to obtain anindication of the acceleration and particularly in airplanes it isdesired to obtain a record of acceleration. In airplanes a record of theacceleration may be made for the entire flight of the craft. In the caseof military craft, the acceleration may vary greatly depending upon themaneuvers through which the craft must operate. In certain of the largercraft a continuous record is kept by automatic recording means ofvarious factors encountered during iiight. Among these factors is thefactor of acceleration. Since the acceleration on military craft,however, may vary appreciably with different craft and with differentmissions on which a craft may operate, it is desired to provide anaccelerometer suitable for installation in various types of craft whichhowever will have the proper degree of damping so as to obtain anaccurate record of the acceleration.

In order to provide for uniformity of records and for a minimum numberof types of apparatus for different craft, there is provided inaccordance with the lpresent invention, an accelerorneter of themechanical type which is provided with adjustable means for controllingthe degree of damping. Therefore if a particular type of craft is to besubjected to high rates of acceleration a greater degree of damping maybe provided for the accelerometer than in other craft which will not besubjected to as great acceleration.

It, therefore, is an object of the present invention to provide a simplecompact accelerometer for use in obtaining an acceleration record.

It is a still further object of the present invention to provide animproved accelerometer in which the degree of damping may be controlledselectively.

Other and further objects of the present invention subsequently willbecome apparent by reference to the following description taken inconnection ywith the accompanying drawing wherein Figure 1 is a frontView of an apparatus constructed in accordance with the presentinvention;

Figure 2 is a side View partially broken away to show the interiorconstruction;

Figure 3 is a top view of the apparatus shown in Figure 1; and

Figure 4 is a partia1 side view showing the side opposite to that shownin Figure 2.

In accordance with the present invention there is provided anaccelerometer having a support or mounting frame II which is adapted tobe secured to a supporting surface in a craft such as an vairplane by aplurality of mounting screws I2. Secured in a suitable manner to thesupporting plate II are a pair of posts I3 and I4 which if desired maybe formed as an integral portion of the supporting plate II. Secured tothe top of the posts or post portions I3 and I4 is a top plate I5.Secured to the bottom portions of the posts I3 and I4 is a bottomplateI6. Adjacent the forward edge of the top and bottom plates I5 and I6 area plurality of posts I1 and I8 and serve to form the main frame of theapparatus. The lower ends of the posts I1 and I8 are secured in.position vby screws I9 and 2| which pass through a depending apron orbracket portion 22 positioned beneath the bottom plate I8. Between theupper and lower plates I5 and I6 two similar metal bellows 23 and 24 aremounted with an interconnecting weight 25. The outer ends of the bellows23 and 24 are secured to the upper and lower plates I5 and I6respectively in a manner as to hold the bellows ends rigidly inposition. Any suitable manner of fastening may be utilized.

The upper end of the upper bellows 23 is secured to an end member 21 asfor example by soft soldering. The end member 21 has a threaded aperture28 for receiving the threaded end of a mounting cap screw 2S whichextends through a suitable aperture in the top plate I5.

The bottom end of the lower bellows'24 is connected to a lower member 3Iwhich is provided with a downwardly extending threaded portion or nipple32 which passes through a suitable opening in the lower plate I6. Thenipple 32 is engaged by a lock nut 33 so as to rigidly secure the member3| in position relative to the lower mounting plate I6. Mounted betweenthe upper cap screw member 29 and the nipple 32 is a hollow rod 34having adjacent its upper end an opening 35. Beneath the weight 25 thehollow rod 34 has another opening 36. The opening 36 is adapted to beopened or closed to a certain degree by an adjustable tapered plug 31which extends through the threaded sleeve or nipple 32 and is engaged bya bale gear 38. The end of the tapered plug 31 rests upon a leaf spring39 secured in position in the bottom of the apron or depending bracket22. The gear 38 is engaged by 55 a baffle gear 4I mounted upon aV shaftl42 positioned within a bearing sleeve 43. The shaft 42 is provided withan enlarged slotted head 44 so that the shaft may be rotated by asuitable tool such as a screw driver. Mounted between the bearing 43 andthe gear 4I is a biasing spring 45 which maintains the gear 4l inengagement with the gear 48. Y

The weight 25 mounted between the upper and lower bellows 23 and 24 hasa central opening through which the hollow shaft 34 passes. The centralopening 46 is provided with sufficient clearance as to preclude anypossibility of a frictional contact between the weight 25 and the tube34. At the top and at the bottom of the weight..

extending portions 41 and 48 of the weight are provided for carrying aplurality of radially? ar-V ranged ball bearings 49. therefore operateto position the weight 25 relative to the central tube or shaft 34 in amanner to provide a minimum of friction when the weight. 2,5 moves :inresponse to acceleration or deceleration.. The; rotation of the taperedlplug. 351-Y by the gear 3% causes the opening 36 to be increased ordecreased sothat the air whichy will pass fromonev bellows; to anotheras the weight 2,5. moves upwardly ordownwardly is controlled. If itisassumed that the weight 25 is moved upwardly thel air is: compressed inthe upper bellows 23 which causesthe air to pass through the slightclearance. in the opening 46 and through the'. openingY 35 in thehol-low shaft 34'. rlhe air passing through the opening- 35 leavesthrough the opening 3.51 and entersinto the lower bellows 24'.l The rateat which the air may pass from one bellows: toy another thereforecontrols the degree of damping of the movement of the weight 25. Theweight 251 is provided adjacent its left side with a flattened surface5l to` whichis secured a bimetal arm 52 having `a pin 53 in engagementwith a slot V54- in alever arm 55. The bimetal' arm 52'r moves the pin53 deeper in the slot 54 wi'thydecreasedV temperaturel and thusincreases Vthe 'mechanical ratio of the lever system when thetemperature is lowered. This change Vin -the mechanical lever ratio`compensates forthe increase in elastic modulus or` stiffening f. thebellows with lowered temperatures. With increased temperatures the arm52' moves the pin 53 outward in, the sloty 54. "VThge lever arm 55j ispivotally mounted `on va rotatable shaft 56 carried between two suitablebea-ring inserts 1 and 58 positioned in the iront p osts I1 and'Iii-respectively. The shaft 55 which is journaled between the bearingmembers 5T and 58jhas1 secured thereto a lever 59 which adjacent itsupper end` has Ya counterweight 6l. The lower end: of the lever `59eng-ages a lever rod 62 mounted'fin; a collarV 83? which is secured toan upright sha-ft 64. The lever 59 is interconnected with the rod 62' byone end of a spring 55. The shaft 64' is mounted.A in suitable bearingmembers 66 and '61' andthe top andV bottom plates l5 and I6respectively. The sha-ft 64" has, a reduced dia-meter portion 68extending appreciably above the upper plate l5. v

The-reduced portion 68 of the shaft 64 is adapted to receive a markinglever which engages recordy paper driven by a suitable mechanism toprovide a continuous record of the action ofthe accelerometer unit.V

Sincel the record driving mechanism and the recording stylus orY markingarm do not necessarily constitute a portion of the presentinventionno-further reference thereto need be madev since any-'suitablerecord driving means` and any' The ball bearings. 49-

.4 suitable recording arm, pen, or stylus may be employed.

The shaft 64 also has adjacent its lower end a reduced diameter portion1| which has secured thereto a collar 13. The collar 13 has connectedthereto one end of a spiral spring 14 which has its other end connectedto a stud 15 mounted underneath the bottom plate I6. The spiral spring14 operates -to return the shaft 68 to its null or zero position; i i Ig The operation acceleration or' deceleration acts upon the mass of theweight 25 so as to move the weight upwardly or downwardly so that thepin 53 iinthe slot 54 produces an angular movement of the lever arm 55.The lever arm 55 rotates the shaft 56 tol which is secured the levervarm 59. llh-e lever arms` 59 .turn is coupled to the cross pin or lever62 connected to the vertical shaftV 64 has a reduced end portion 68extending above the top plate I 5 for producing a permanent record. l Y

If themovement of the mass of the weight 2.5-is. too great upon theapplication of a certain acceleration force, this may be damped byadjusting the member 44 which moves the tapered wedge 31 relative totheair hole; 3.6.L If onthe other hand a greater degree of sensitivity isdesired for certain purposes., the wedge 3.1 maybe adjusted so as to.obtain themaximum opening'of the hole 35. Y l

While for the purposeof describing and illus-- trating the presentinvention, apreferred em-V bcdment has been shown in the drawing, it isto, be understood that various modifications may be made therein, and inthe *in-strumentalities and,

components involved without departing from the spirit and scopeof theinvention as defined ir-r the appended claims. Y

This invention is. hereby` claimed as follows:

1. In an accelerometerY comprising a pair .of parallel spaced apartsupport members', a pair of coaxially arranged bellows interconnectedbya weight, said beliows being connected to said sup.-

port members, thev combination comprisingja hol-` low shaft extendingwithin saidy bellows between. said support members, a pluralityv ofapertures .in said shaft; leach aperturebeing associated with ad'iierentv one of said bellows. and adjustable'. means toregulate the.eiectiv-e openingv of at least one'of said apertures to contr-oi thedamping of the movement of' said weight.

2. Inan accelerometer comprising: apair of sup-A` port members arranged'in spaced apart parallel relation, a weight having a central aperture,Va pair of bellows each mounted between said weightl and one of saidsupport` members, the combination comprising a hollow shaft mountedwithin the aperture of'said weight and extending between said supportmembers, said shaft being provided: with a pair of apertures, eachaperture being associated' with a different one of said bellows,adjustable means to regulate the effective opening of one of saidapertures, and bearing means mounted on each'. Vside ofsai'd weightwithin said bellows and in engagement with said hollow shaft to limitthe motionl of said'weight to either of two opposite directions.

3. An accelerometer comprising a pair -of parallel spaced aparthorizontal support members, a pair of coaxial: bellows connected to saidsupport members, an apertured weight connected between said supportmembers, a shaft'mounted within the aperture of sai'd'y weight inlcoaxial relationto said weight and said bellows,` a plurality of bear-`ings mounted on opposite sides of said' weight within said bellows andarranged to engage said weight to limit movement thereof to axialdirections with a minimum of friction, a iluid passage interconnectingsaid bellows, adjustable means for controlling the rate of flow of uiclthrough said passage including a control mechanism mounted beneath saidweight and bellows, means for actuating a record producing element, andmechanical means interconnecting said latter means and said weight.

4. An accelerometer comprising a pair of parallel spaced aparthorizontal support members, a pair of bellows arranged coaxially andeach secured to one of said support members, a weight mounted betweensaid bellows, guide means for said weight extending between saidparallel support members in coaxial relation to said weight and bellows,a plurality of friction reducing bearing members mounted on oppositesides of said weight within said bellows and in engagement with saidguide means to limit movement of said weight to axial directions, acoaxial uid passage within said guide interconnecting said bellows,adjustable means coaxially arranged relative to said weight forcontrolling the rate of flow of iluid through said passage, andmechanical means connected to said weight for translating reciprocablemovement thereof into angular rotary movement.

5. An accelerometer comprising a pair of parallel spaced aparthorizontal support members, a pair of bellows arranged in coaxialrelation and secured to said support members, a weight interposedbetween said bellows and secured thereto,

guide means extending between said parallel support members in coaxialrelation to said weight and bellows, a plurality of bearing membersmounted on said weight and in engagement with said guide means to limitmovement of said weight to axial directions, a uid passage within saidguide means for interconnecting said bellows, means extending below thelower support member and arranged coaxial to said passage forcontrolling the rate of ow of fluid through said passage, a rotatableshaft adapted to actuate a record producing element, and mechanicallinkage means interconnecting said shaft with said Weight whereby saidshaft will be moved in proportion to the movement of said weight.

6. An accelerometer comprising a pair of parallel spaced aparthorizontal support members, a pair of bellows arranged in coaxialrelation and secured to said support members, a weight interposedbetween said bellows and secured thereto, guide means extending betweensaid parallel support members in coaxial relation to said weight andbellows, a plurality of bearing members mounted on said weight withineach of said bellows and in engagement with said guide means to limitmovement of said weight to axial directions, a uid passage within saidguide interconnecting said bellows, coxial means within said passage forcontrolling the rate of ow of uid through said passage, a rotatableshaft adapted to actuate a record producing element, mechanical linkagemeans interconnecting said shaft with said weight whereby said shaftwill be moved in proportion to the movement of said weight, and meanstending to restore said shaft and said weight to null position.

7. In an accelerometer comprising a pair of parallel spaced apartsupport members, a pair of coaxially arranged bellows interconnected bya weight, said bellows being connected to said support members, thecombination comprising a hollow shaft extending within said bellowsbetween said support members, a plurality of apertures in said shaft,each aperture being associated with a different one of said bellows, andadjustable means mounted on one of said support members for regulatingthe effective opening of at least one of said apertures to control thedamping of the movement of said weight.

8. In an accelerometer comprising a pair of parallel spaced apartsupport members, a pair of coaxially arranged bellows interconnected bya weight, said bellows being connected to said support members, thecombination comprising a hollow shaft extending within said bellowsbetween said support members, a plurality of apertures in said shafteach associated with a different one of said bellows, and adjustablemeans mounted on one of said supports including a rotatable valve memberfor controlling the effective opening of at least one of said aperturesthereby to regulate the damping of the movement of said weight.

CLAUDE M. HATHAWAY.

REFERENCES CITED The following references are of record in the ile ofthis patent:

UNITED STATES PATENTS Number Name Date 2,194,624 Titterington Mar. 26,1940 2,317,028 Chappell Apr. 20, 1943 FOREIGN PATENTS Number CountryDate 672,042 France Dec. 21, 1929

